This proposal seeks support for the analysis of interview data collected in Brazil during 1972-73. The data consist of three samples: interviews with 275 elites (higher civil servants, senators and deputies, industrialists and financiers, trade union presidents, bishops, and leaders of associations in the liberal professions); a multistage probability sample (n equals 1,330) of the population in six states of the Center-South; a systematic random sample of 330 trade union members in 12 of the largest unions in Rio and Sao Paulo. Most of the analysis entails the testing of two complementary models of public opinion concerning government policy about birth control. One model is "structural": it involves a comparison of individual preferences about birth control policy with the policy preferences of groups as perceived by others outside these groups. The joint distribution of individual attitudes and mutual perceptions constitutes the structure of policy preferences. Application of this approach also generates estimates of group behavior which are more accurate than those usually obtained by attempting to predict the behavior of individuals from their attitudes. The other model is substantive. It relates preferences on birth control to preferences on other issues of political importance in order to determine the presence of ideologies as belief systems. Testing of this model enables us to understand better the political context and possible side-effects of various policy alternatives with respect to birth control. The structural and substantive models are integrated in terms of a model of political control, which hypothesizes that public policy issues are manipulated in order to increase political legitimacy.